[Minor] Remove unused val in Master

Author: Andrew Or <andrewor14@gmail.com>

Closes #1365 from andrewor14/master-fs and squashes the following commits:

497f100 [Andrew Or] Sneak in a space and hope no one will notice
05ba6da [Andrew Or] Remove unused val

core/src/main/scala/org/apache/spark/deploy/master/Master.scala

@@ -72,9 +72,7 @@ private[spark] class Master(
   val waitingApps = new ArrayBuffer[ApplicationInfo]
   val completedApps = new ArrayBuffer[ApplicationInfo]
   var nextAppNumber = 0
-
   val appIdToUI = new HashMap[String, SparkUI]
-  val fileSystemsUsed = new HashSet[FileSystem]
 
   val drivers = new HashSet[DriverInfo]
   val completedDrivers = new ArrayBuffer[DriverInfo]
@@ -159,7 +157,6 @@ private[spark] class Master(
       recoveryCompletionTask.cancel()
     }
     webUi.stop()
-    fileSystemsUsed.foreach(_.close())
     masterMetricsSystem.stop()
     applicationMetricsSystem.stop()
     persistenceEngine.close()

python/pyspark/java_gateway.py

@@ -56,7 +56,7 @@ def launch_gateway():
             (stdout, _) = proc.communicate()
             exit_code = proc.poll()
             error_msg = "Launching GatewayServer failed"
-            error_msg += " with exit code %d!" % exit_code if exit_code else "! "
+            error_msg += " with exit code %d! " % exit_code if exit_code else "! "
             error_msg += "(Warning: unexpected output detected.)\n\n"
             error_msg += gateway_port + stdout
             raise Exception(error_msg)